100 years of change in an old-growth Scots pine forest in Hamra National Park: insights from permanent plots established in central Sweden in 1922

Hamra National Park in the province of Dalarna in central Sweden was established in 1909 to protect a unique unlogged old-growth forest. In 1922, Henrik Hesselman set up two permanent plots in Hamra to be able to follow the development of the forest over time. In 2022, we re-inventoried the Scots pine-dominated plot and found that (1) the number of trees in the plot almost doubled from 593 trees in 1922 to 1013 trees in 2022, (2) Norway spruces are starting to take over the initially Scots pine-dominated plot, (3) the basal area of dead trees has increased by 286% and (4) the variability in annual Scots pine growth has increased over the studied time period. Given this strong deviation from the original state of the forest, we suggest restoring part of the forest to its early-1900s state while allowing the permanent plot to evolve naturally.